I made a repair, then, uninstalled and re-installed Office 2016.
I tried different keyboards. I copied and pasted the content to a new document.
None of them worked.
The common thing when this happens that I observe I am pressing my right finger on right Shift key on keyboard. By the way, I listed and removed all shortcut key combinations that can open save as box in Word 2016.
PS: No problem with printing.
Windows 10 Home Single Language,
21H1,
19043.1110
Windows Feature Experience Pack 120.2212.3530.0
PS 2: My main keyboard is Logitech G613 wireless mechanical keyboard.